Foodborne illness affects more than 76 million Americans each year with an estimated cost of 1.4 billion dollars in lost human productivity, medical expenses and increased animal production costs in the United States alone (FoodNet, 2002; Madie, 1992). Salmonellosis contributes 36% of this incidence. With the increased resistance of bacteria to anti-microbials and the withdrawal of antibiotics, such as the fluoroquinolones, from use in poultry production by the Food and Drug Administration, effective alternative treatments for prevention and treatment of bacterial diseases must be developed. Strain-specific bacteriophage therapy has been suggested as an alternative to antimicrobials for the control of bacterial diseases, such as Salmonellosis, in animals and man (Slopek et al., 1987; Smith and Huggins, 1982, 1983; Park et al., 2000, Huff et al., 2001).
Bacteriophages are members of a specific group of viruses that only infect and replicate in bacteria, and have no potential to infect animals or plants. Replication of the bacteriophage can result in lysis and death of the host bacterial cells. Bacteriophages are ubiquitous and can be found in water, sewage or soil. Bacteriophages are characterized as extremely host specific and will often infect and replicate in only one bacterial species or only a single serotype within a species. This specificity of the bacteriophage for a particular host bacterium has been utilized in classifying bacteria, but has been a limiting factor in using bacteriophage to kill bacteria and treat or prevent the spread of bacterial diseases. There have been numerous attempts, with some success, to use bacteriophages to treat bacterial infections (Slopek et al., 1987; Smith and Huggins, 1982, 1983; Park et al., 2000, Huff et al., 2001). However, commercial use of bacteriophages for treatment of infections has not gained widespread acceptance in part due to the need to identify an effective and strain-specific bacteriophage for each disease outbreak.
The use of bacteriophages for therapy or decontamination purposes has been limited for several reasons, including strain specificity of some bacteriophage. Strain specificity requires that the bacteria are identified and the susceptibility of the bacteria to the bacteriophage assessed before using the bacteriophage. This process is time-consuming and costly. Additionally, bacteriophages require bacteria for growth and thus it is often difficult to ensure removal of the bacteria from the bacteriophage preparation. This is especially problematic if the bacteriophage only grows in pathogenic bacteria. In addition, it has proved difficult to deliver large numbers of bacteriophages to the sites of infection. For example, bacteriophages are lost as they travel through the upper gastrointestinal tract, which has uniformly resulted in the need for administration of large numbers of bacteriophages for the treatment of enteric infection. Thus, bacteriophage therapy while promising has not proved useful due to these limitations.